Heat assisted magnetic recording (HAMR) generally refers to the concept of locally heating a recording medium to reduce the coercivity of the medium so that an applied magnetic writing field can more easily direct the magnetization of the medium during the temporary magnetic softening of the medium caused by the heat source. The heated area in the storage layer determines the data bit dimension. A tightly confined, high power light spot is used to heat a portion of the recording medium to substantially reduce the coercivity of the heated portion. Then the heated portion is subjected to a magnetic field that sets the direction of magnetization of the heated portion. In this manner the coercivity of the medium at ambient temperature can be much higher than the coercivity during recording, thereby enabling stability of the recorded bits at much higher storage densities and with much smaller bit cells. Heat assisted magnetic recording is also referred to a thermally assisted magnetic recording.
Near-field transducers can be used to focus light to a small spot. An efficient means for concentrating light with a near-field transducer would be beneficial in HAMR recording heads.